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Publication Abstract from PubMed

Periplasmic substrate binding proteins (SBPs) bind to the specific ligand with high affinity and mediate their transport into the cytoplasm via the cognate inner membrane ATP binding cassette (ABC) proteins. Because of very low sequence identities, understanding the structural basis of substrate recognition by SBPs has remained very challenging. There are several structures available for the ligand bound sugar SBPs but very few unliganded structures are reported. No structural data is available for sugar SBPs from Pseudomonas sp. till date. This study reports the first high resolution crystal structures of periplasmic glucose binding protein from Pseudomonas putida CSV86 (ppGBP) in unliganded form (2.5 A) as well as complexed with glucose (1.25 A) and galactose (1.8 A). Asymmetric domain closure of ppGBP was observed upon substrate binding. The ppGBP was found to have an affinity of ~ 0.3 microM for glucose. The structural analysis showed that the sugars are bound to the protein mainly by hydrogen bonds and the loss of two strong hydrogen bonds between ppGBP and galactose compared to glucose may be responsible for lowering its affinity towards galactose. The higher stability of ppGBP-glucose complex was also indicated by 8 degrees C increase in the melting temperature compared to unliganded form and ppGBP-galactose complex. ppGBP binds to monosaccharide but the structural features revealed it to have an oligosaccharide binding protein fold indicating that during evolution the sugar binding pocket may have undergone structural modulation to accommodate monosaccharide only.

High resolution structures of periplasmic glucose binding protein of Pseudomonas putida CSV86 reveal structural basis of its substrate specificity.,Pandey S, Modak A, Phale PS, Bhaumik P J Biol Chem. 2016 Feb 9. pii: jbc.M115.697268. PMID:26861882^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.